The present invention relates to a lighting system and a liquid crystal display using the lighting system, which is used for televisions, personal computers, etc.
In these years, the liquid crystal display widely used for the televisions, personal computers, etc. has a major feature such that its size of depth is small, or a thin type as a flat panel display, in comparison with a cathode-ray tube display device which is known as emitted an electron ray.
For a purpose of further applying the feature of thin type, the liquid crystal display uses a backlight system in which a light source is arranged on the rear of screen, in the past, to transmit a light through a liquid crystal portion to be controlled by a voltage. In these days, the liquid crystal display has also employed a sidelight-type backlight system in which a light source is arranged on the both sides of a screen to reflect diffusely the light from the both side light sources and to lead the light as a surface light source from the rear of liquid crystal portion by using a light guide plate.
For example, JP-A-9-148633 (referring to paragraph numbers 0018 to 0020, 0024, 0025, FIG. 1, and FIG. 2) discloses a technique with a printed-circuit board forming an electrical conductive circuit, a plurality of light-emitting diode chips arranged linearly on a predetermined location of the electrical conductive circuit, a pair of white-based resin bodies formed on both sides thereof in parallel, and a transparent resin body to seal the light-emitting diode chips arranged linearly between the white-based resin bodies. In this way, the light emitted from the light-emitting diode chip is reflected by the white-based resin body and is focused on an optical axis of the light source, enhancing usability of the light.
Incidentally, the JP-A-9-148633 uses a white light-emitting diode as a light source, therefore, there is a problem that a color purity cannot be made high since a color of display screen is produced by a color filter alone, which is arranged in parallel and overlapped with the liquid crystal portion.
Further, since the light sources are arranged on the sides, it is difficult that the light emitted from the light-emitting diode of the light source is turned into a light to be transmitted through the liquid crystal portion perpendicular to a transmitted light direction, after the emitted light from the light-emitting diode is transmitted with a less loss through the transparent resin body covered on the light-emitting diodes. Therefore, it is desirable that the light emitted from the light-emitting diode of the light source is led to the liquid crystal portion with the less loss. Further, in the case where the light-emitting diode chip is mounted by a flip-chip connection with the electrical conductive circuit on the printed circuit board, it is necessary to provide an expensive production line for enhancing accuracy because of using a sputtering, photolithograph, etc.
In addition, in the case where an electrical conductive pattern on the printed circuit board is long for connections of the mounted light-emitting diode chips, an occupied area on the printed circuit board becomes broaden. A tendency not to effectively use the light from the light source causes due to a low light reflectance of the electrical conductive pattern since the light reflectance of the conductive pattern is low.